Surgery – Body rests – supports or positioners for therapeutic purpose
Reexamination Certificate
1999-04-02
2001-05-15
Brown, Michael A. (Department: 3764)
Surgery
Body rests, supports or positioners for therapeutic purpose
C128S897000
Reexamination Certificate
active
06230710
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an electrical power system which provides power to various medical devices, and more particularly to an electrical power system which receives power from an internal and various external power sources and provides uninterrupted power for use in a self-contained transportable life support system, which is utilized in the resuscitation, stabilization, and transport of medical patients such as heart attack, stroke, accident victims and battlefield casualties.
BACKGROUND OF THE INVENTION
The need for simultaneously transporting and providing necessary medical treatment to patients in emergency conditions is well known. Such need can be met with a self-contained transportable life support system which integrates various medical and utility devices into a stretcher upon which a patient is placed.
An example of such system is described in the related patent application Ser. No. 08/667,693 filed on Jun. 21, 1996, entitled SELF-CONTAINED TRANSPORTABLE LIFE SUPPORT SYSTEM.
In order to evacuate a patient from the battlefield to a remote hospital, a number of different military vehicles are commonly used. For example, a HumVee may be used to transport the patient to a helipad, where the patient is subsequently transported via a UH-60 Blackhawk or UH-1 Huey helicopter to an airfield. From the airfield, the patient is then transported typically via a C-130 or C-141 fixed wing aircraft to an airport near the remote hospital. Thus, it is desirable that such self-contained transportable life support system can draw electrical power from various external power sources, such as those which exist in these transport vehicles. It is desirable that the power connection to any external power source is designed to be foolproof, in order to prevent human error. It is also desirable that such system can be powered by a rechargeable internal power source when no external power source is available.
It is imperative that the switching from one type of power source to another does not interrupt the electrical power being delivered to the load of medical and utility devices of the life support system, so that the ongoing medical care is not impeded.
In addition, it is desirable that any failure of one medical or utility device in such life support system will not interfere with the operation of the remaining functioning devices.
The present invention discloses an electrical power system, to be used in a self-contained transportable life support system, which allows such life support system to possess the desired features discussed above.
SUMMARY OF THE INVENTION
A switching control circuit for use in an electrical power system for a transportable life support system is disclosed. The switching control circuit provides uninterrupted power to a load of medical and utility devices by switching between one of a set of converted external power voltages and an internal power voltage outputted by a rechargeable internal power source. The power switching is effected within the time interval during which a residual power voltage still remains on line due to capacitance discharge of the corresponding power converter and capacitance discharge of the load, resulting in uninterrupted electrical power to the load.
The switching control circuit comprises: (a) an input power select circuit for outputting a voltage selected from the group of internal and converted external power voltages; (b) a main bus switch, for controlling the application of the selected voltage to the load; and (c) a main bus for transporting the selected voltage to the load of medical and utility devices.
The input power select circuit monitors the active converted external voltage to determine its magnitude with respect to a threshold voltage. When the converted DC voltage is larger than a threshold voltage, the circuit selects the converted voltage instead of the rechargeable internal power source. When it falls below the threshold voltage, the circuit selects and outputs the rechargeable internal power source. This voltage selection scheme facilitates seamless switching between the rechargeable internal power source and one of the converted external power sources. External power cabling allows for the application of only one external power source at a time. Thus, only one power converter is active at a given time.
The input power select circuit preferably comprises a boost regulator circuit which creates an enhancement voltage that is greater than the selected voltage by a fixed amount of voltage and utilizes the resulting enhanced voltage to control the main bus switch. In the preferred embodiment of the invention, the boost regulator circuit creates an enhanced voltage that exceeds the selected voltage by approximately 12 volts.
The input power select circuit comprises (a) a diode OR gate for preventing contention between the converted external power source and the rechargeable internal power source; (b) a battery control circuit which compares the diode OR gate output described in (a) above with a threshold voltage and enables the rechargeable internal power source to output the internal power voltage to the bus switch when the diode OR gate output is smaller than the threshold voltage.
A converted external power voltage produced by the active power converter is approximately 6 volts greater than the threshold voltage internal to the battery control circuit. Thus, when the converted external power voltage falls below the threshold voltage, this indicates that the corresponding power converter has just been disconnected from an external power source or the power converter has failed. Capacitors residing in the power converter and capacitors residing on the main bus will hold the main bus voltage up briefly while switching to the rechargeable internal power source is accomplished.
In the preferred embodiment of the invention, the threshold voltage is set at approximately 6 volts less than the nominal value of a converted external power voltage. This allows the input power select circuit to select the rechargeable internal power source, during the brief hold up time of the main bus, while the capacitance of the corresponding power converter and the capacitance of the main bus are discharging. This results in uninterrupted electrical power to the load during the voltage switching.
The bus switch is preferably a field-effect transistor (FET) switch.
The switching control circuit also includes a main bus delay circuit for controlling turn ON of the main bus switch. The main bus delay circuit receives the rising edge of the selected voltage from the input power select circuit and controls operation of the bus switch at initial power-up of the transportable life support system. By controlling the bus switch, the main bus delay circuit delays application of the selected voltage to the main bus by a fixed amount of time at initial power-up to prevent fire hazard.
This time delay is about ten seconds. During this time delay, a brushless fan is operated to dissipate any flammable gas build-up in the transportable life support system, before main bus power is applied. This delay prevents potential fire hazard.
An electrical power system for providing uninterrupted power, by switching between different power sources, to a load of medical and utility devices in a transportable life support system, is also disclosed.
The electrical power system comprises: (a) a set of external power sources which provide different external power voltages; (b) a rechargeable internal power source which provides an internal power voltage; (c) a set of different power converters which convert the different external power voltages into converted external power voltages, one of the different power converters providing recharge power to the rechargeable internal power source; (d) a switching control circuit which receives the internal and converted external power voltages, and switches at its output between the internal power voltage and one of the converted external power voltages without power interruption to the loa
Alford Thomas Holland
Good Thomas Wakefield
Sobko William Richard
Brown Michael A.
Integrated Medical Systems, Inc.
Stetina Brunda Garred & Brucker
LandOfFree
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